Scalp and face with their sensory innervation

The scalp is the part of the head that extends from the superciliary arches anteriorly to the external occipital protuberance and superior nuchal lines posteriorly. 

Laterally it continues inferiorly to the zygomatic arch. 

The scalp is a multilayered structure with layers that can be defined by the word itself:

• S-skin

• C-connective tissue (dense)

• A-aponeurotic layer (galea aponeurotica)

• L-loose connective tissue

• P-pericranium

The first three layers are tightly held together, forming a single unit.

• This unit is sometimes referred to as the scalp proper and is the tissue torn away during serious 'scalping' injuries. 

• Skin is thick, hair bearing and contains numerous sebaceous glands.

• Connective tissue is fibrofatty, the fibrous septa uniting the skin to the underlying aponeurosis of the occipitofrontalis muscle. Numerous arteries and veins are found in this layer. The arteries are branches of the external and internal carotid arteries, and a free anastomosis takes place between them.

• Aponeurosis (epicranial) is a thin, tendinous sheet that unites the occipital and frontal bellies of the occipitofrontalis muscle. The lateral margins of the aponeurosis are attached to the temporal fascia.

• Loose areolar tissue occupies the subaponeurotic space and loosely connects the epicranial aponeurosis to the periosteum of the skull (the pericranium). The areolar tissue contains a few small arteries, but it also contains some important emissary 

veins. The emissary veins are valveless and connect the superficial veins of the scalp with the diploic veins of the skull bones and with the intracranial venous sinuses. 

Called dangerous layer of scalp-emissary veins open here and carry any infections inside the brain (venous sinus)

 Bleeding lead to black eye.

• Pericranium, which is the periosteum covering the outer surface of the skull bones.

Muscle of the Scalp anteriorly, an occipital belly posteriorly, and an aponeurotic tendon (epicranial aponeurosis) connecting the two.

• It is from two major sources, cranial nerves or cervical nerves, depending on whether it is anterior or posterior to the ears and the vertex of the head.

Anterior to the ears and the vertex

• Supratrochlear nerve

• Supraorbital nerve

• Zygomaticotemporal nerve

• Auriculotemporal nerve

By branches of all four divisions of the trigeminal nerve

Posterior to the ears and the vertex

• Great auricular nerve

• Lesser occipital nerve

• Greater occipital nerve

• Third occipital nerve

By branches of all four divisions of the spinal cutaneous nerves (C2 and C3)

• Arteries supplying the scalp are branches of either the external carotid artery or the ophthalmic artery which is a branch of the internal carotid artery.

• External carotid arteries

• Occipital arteries

• Posterior auricular arteries

• Superficial temporal arteries

• Internal carotid arteries

• Supratrochlear arteries

• Supraorbital arteries

• Veins draining the scalp follow a pattern similar to the arteries.

• Of the deep parts of the scalp 

– Via emissary veins that communicates with the dural sinuses.

• Lymphatic drainage of the scalp generally follows the pattern of arterial distribution.

• The lymphatics in the occipital region initially drain to occipital nodes which drain into upper deep cervical nodes.

• Lymphatics from the upper part of the scalp drain in two directions:

• Posterior to the vertex of the head they drain to mastoid nodes.

• Anterior to the vertex of the head they drain to pre-auricular and parotid nodes.

Face :

Boundaries

• Extends superiorly to the hair line, inferiorly to the chin and base of mandible, and on each side to auricle

• Forehead is common to both scalp and face.

• Very vascular

• Due to rich vascularity face blush and blanch.

• Facial skin is rich in sebaceous gland and sweat gland.

• Wounds of face bleed profusely but heal rapidly.

• Sebaceous gland keep the skin oily but also cause acne in adult.

• Called muscle of facial expression and lie in superficial fascia.

• Embryologically they develop from mesoderm of 2nd branchial arch, therefore supplied by facial  nerve.

• No deep fascia is present in the face.

Muscles of the Face 

(Muscles of Facial Expression)

• The muscles of the face develop from the 2nd pharyngeal arch and are innervated by branches of the facial nerve [VII]. 

• They are in the superficial fascia, with origins from either bone or fascia, and insertions into the skin.

• these muscles control expressions of the face.

• They act as sphincters and dilators of the orifices of the face (i.e. the orbits, nose, and mouth). 

• Orbital group

• Nasal group

• Oral group

• Other muscle groups

• Two muscles are

– Orbicularis oculi

– Corrugator supercilii

• 3 parts-

• Orbital part(outer)

– Originate from medial part of medial palpebral ligament and form concentric rings, return to point of origin

    Action –closes the lids tightly

• Palpebral part(Inner)

– Originate from lateral part of medial palpebral ligament

– Insert into lateral palpebral raphe

     Action-closes the lids gently

• Lacrimal part(Small)

– Originate from lacrimal fascia& lacrimal bone

– Insert into upper &lower tarsi

     Action-dilate lacrimal sac